"At this point, I was sick of feeling like a milk machine," the 32-year-old Lachey wrote. "I loved my bonding time with Camden. ... But also there were times when he was crying of hunger. ... Then when Camden was done eating, I wasn't able to lay and cuddle with him.

"I had to give him back to all the well-wishers who wanted to hold him and love him, and I sat and waited for the next feeding, where I would do it all again," she added.

Lachey said that despite her husband Nick's support, she felt alone.

"I started crying. I was feeding Camden and crying my eyes out. I felt like I had officially come undone," Lachey wrote.

After handing off the baby to her husband, Lachey took a ride around the block, stopped by Starbucks and finally came home to shower and gather herself. Then, she apologized to Nick Lachey.

"I was sorry for the weeks of losing myself. I was sorry for the weeks to come when I won't be myself, and I am sorry I can't do it all like I thought I could," she wrote.

But she isn't the first Hollywood mom to open up about postpartum depression. Read below to see other stars who've been vocal about it.

Brooke Shields

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Brooke Shields is perhaps the most outspoken celebrity on postpartum. In 2007, she opened up to ABC News about her depression after giving birth to her first daughter in 2003.

"We are taught that being a mother and becoming a mother is the most glorious thing you could ever do. It's the most natural thing," she said. "If you don't do this beautifully, then you are wrong. You know, you're not a good mother. You're not a good woman."

The action star later apologized, telling "Today" show host Matt Lauer, "It's not what I intended. In looking at myself, I thought, 'Man, that came across as arrogant.' ... That's one of those things you go, 'OK, I could have absolutely handled that better.'"

In order to shed light on the illness and her struggle, Shields wrote a book titled, "Down Came the Rain: My Journey Through Postpartum Depression."

Gwyneth Paltrow

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(Getty)

Gwyneth Paltrow opened up about her postpartum depression in one of her weekly GOOP newsletters on her website that she created to "share all of life's positives."

"When my son, Moses, came into the world in 2006, I expected to have another period of euphoria following his birth, much the way I had when my daughter was born two years earlier," the now-40-year-old wrote on her website. "Instead, I was confronted with one of the darkest and most painfully debilitating chapters of my life. For about five months, I had what I can see in hindsight as postnatal depression, and since that time, I have wanted to know more about it. Not only from a hormonal and scientific standpoint, and why so many of us experience it, but from the perspective of other women who have gone through it."

Bryce Dallas Howard

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(AP)

"The Help" star Bryce Dallas Howard saw Paltrow as an example and shared her story about suffering from postpartum depression.

The 32-year-old actress wrote on Paltrow's site that she "treasured every moment I had with this new life growing inside me," even in the last month of her pregnancy when she tipped "the scale at over 200 pounds." Then, when Howard gave birth, she said, she "felt nothing."

But through the experience, she learned "never be afraid to ask for help."

Alanis Morissette

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Alanis Morissette said last August that she's always there for her son, Ever, whenever he needs her. But she revealed she suffered "baby blues," an intense struggle with post-partum depression after he was born.

When "Good Morning America's" Lara Spencer asked Morissette why she felt the need to share about this, she said, "I didn't feel the need the share. It just was part of the autobiographical transparency value that I have. I really think transparency really levels the playing field for all of us and renders our humanness OK.

"It was just a really intense time and, if I could share anything with anyone who's going through it, it would be to encourage them to seek help and reach out a little earlier than I did."

"I think the feminist movement went through being very dependent, being autonomous, being individualistic and being empowered on our own, burning your bras as such. And then now, in 2012, there's this gorgeous inner-dependence and saying, 'I'm really empowered and I need you and I need help.' It's really great," the 38-year-old added.

Courteney Cox

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Actress Courteney Cox revealed that she suffered from postpartum depression after giving birth to daughter Coco in 2004. Cox, 48, told USA Today that she did not see immediate effects from the depression.

"I went through a really hard time -- not right after the baby, but when [Coco] turned 6 months, I couldn't sleep," she said. "My heart was racing. And I got really depressed. I went to the doctor and found out my hormones had been pummeled."

Carnie Wilson

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Singer and "The Newlywed Game" host Carnie Wilson gave birth to a baby girl, Lola Sofia, in 2005, but after she gave birth, she told People magazine, "I cried all day over everything."

For Wilson, 44, postpartum gave her the feeling of fear.

"You're so afraid you're going to fail this baby," she said. "What if you drop her or hurt her? She's totally dependent on you and it's scary."

"Medication can help us live a happier life," she said. "However, he's partly right about exercise and vitamins. I do feel better when I'm exercising and eating correctly. But I don't think that will work entirely for everyone. I was lucky."